LOW TEMPERATURE CATHODES FOR CROSSED-FIELD DEVICES.
Final rept. 10 Jun 59-30 Jun 61,
WESTINGHOUSE ELECTRIC CORP ELMIRA N Y ELECTRONIC TUBE DIV
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In seeking a low noise, low temperature, thermionic cathode suitable for use in crossed field microwave devices, eleven different cathodes were examined in detail for their cathode noise properties. These cathodes comprised of five different types of tungsten-based barium dispenser cathodes, two types of nickel matrix cathodes, the conventional oxide coated cathode and three new cathodes. Of these latter, two were platinum-based barium dispenser cathodes and the other a rhenium-based barium dispenser cathode. The noise properties of the cathodes were characterized by measuring their emission fluctuations true flicker effect as a function of frequency, current density and anode dissipation, and by measuring their space charge reduction factors for shot noise and flicker noise. These investigations showed the rhenium-based barium dispenser cathode to be the most promising from the point of view of low noise applications. These studies also proved extremely useful in elucidating the physical nature of noise generation in some of these cathodes. The results on space charge reduction of noise demonstrated that with certain of the cathodes new, but not identified, mechanisms for noise generation other than emission fluctuations become dominant when they are operated space charge limited.
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